1. Field
The invention relates to a display panel, and more particularly to a display panel having a color filter-on-thin film transistor (“COT”) structure.
2. Description of the Prior Art
A display device has been greatly developed with the growth of information communication technology, and has been widely used in the modern life. A liquid crystal display is one of the most widely used types of display device due to desired characteristics such as prominent picture quality, light weight, thin filming, and low driving voltage.
The liquid crystal display typically includes two substrates that face each other at a predetermined distance and liquid crystals interposed between the two substrates. In the liquid crystal display, light leakage may be prevented from occurring by providing a black matrix corresponding to a thin film transistor array. In a conventional liquid crystal display, a substrate, in which a color filter is provided, may be different from a substrate in which a thin film transistor is provided. Accordingly, in such a conventional liquid crystal display, alignment keys may be provided on the respective substrates for accurate alignment, and then the respective substrates are aligned and bonded to each other. However, in such a bonding process, misalignment may still occur between the black matrix, the thin film transistor and wirings to cause the light leakage to occur.
In order to prevent misalignment between the black matrix, the thin film transistor and wirings and to secure an aperture ratio of the liquid crystal display, a liquid crystal display having a color filter on thin film transistor (“COT”) structure, in which a thin film transistor and a color filter are provided in a same substrate, has been developed. The liquid crystal display having the COT structure includes a first substrate, a second substrate facing the first substrate and including a thin film transistor, a color filter and a black matrix therein, and a liquid crystal layer interposed between the first substrate and the second substrate.
The liquid crystal display having the COT structure, when an alignment layer and a seal pattern come in contact with each other in a process of bonding the first substrate and the second substrate, seal coming-off inferiority may occur since a bonding force between the alignment layer and the seal pattern is weak. Further, rubbing directions of the alignment layers provided on the first substrate and the second substrate may be twisted, thereby deteriorating the contrast ratio.
As a result, although the COT structure may improve the aperture ratio through arrangement of the black matrix, the color filter and the thin film transistor on a same substrate, the black matrix may not be provided in the first substrate of the COT structure, but only transparent materials are arranged in the first substrate of the COT structure. Accordingly, it is desired to perform a process of manufacturing an alignment key for preventing such a misalignment.